The Present Perfect Construction in English has the following uses (cf. McCawley 1971):
(a) The Universal sense of the Perfect, used to indicate that a state of affairs prevailed throughout some interval stretching from the past into the present
• I've known Max since 1960.
(b) The Existential sense of the Perfect, used to indicate the existence of past events,
• I have read Principia Mathematica five times.
(c) The Stative/Resultative sense of the Perfect, used to indicate that the direct effect of a past event still continues
• I can't come to your party tonight - I've caught the flu.
(d) The Hot News sense of the Perfect, used to report hot news
• Malcolm X has just been assassinated.
This, coupled with the lack of Present Perfect with subjects who are dead
- Madonna has visited Princeton.
- *Einstein has visited Princeton.
means that X has died is only appropriate at a time when the addressee would not yet know that X is dead.
Executive Summary: If it's Hot News, use the Present Perfect; but if it's Old News, simple past.
McCawley, James D. 1971. Tense and time reference in English.
In C. Fillmore and T. Langendoen (eds.), Studies in Linguistic Semantics
New York: Holt, Rinehart and Winston, pp 96-113.